The Pioneer A06 is an excellent 4x -/+ burner. Better at - burns though. One of its best features is media compatibility... it will burn just about anything you can throw at it.
The LiteOn LDW-401S is also excellent. It is a better + burner. It's a little more finicky with the media, but LiteOn keeps pumping out the firmware for max compatibility.
Both are great choices, IMHO.